Is it international to international? What class flying? I assume different carriers or separate tickets involved is why you're having to do this? FWIW I posted same question but with a 1 hour 40 minute time. Replies said that it was doable without delays to the inbound flight. But my arrival would be at 11:30 p.m. and apparently that's not the busiest time, but it's still going to be a nail biter with the time I have. I was told to ensure that I already had a Turkish eVisa to clear immigration. Good luck, but from the replies I got it would seem that 45 minutes is possibly impossible unless you are the VIP head of state of another country trying to do this. Check the history of your inbound flight's arrival time. Calculate from the time the plane lands then add time to taxi to gate, add in extra time if the plane parks at a remote stand and you're bused in, add time to walk to immigration, time to clear immigration, time for your luggage to arrive on the carousel, time to clear customs (pretty quick if nothing to declare), time to walk upstairs to check-in counter, time to recheck bag (flying J or F?, if Y the line could be long), time to walk to security, to clear security, to clear immigration again, to walk (or sprint) to gate. Whew! If you manage to do this you'd qualify to be in the next Mission Impossible movie. Oh, and make sure you have the map of the terminal in your head, and on hand to navigate quickly.